Semiconductor devices are provided. A semiconductor device includes a fin structure having a plurality of first semiconductor patterns and a plurality of second semiconductor patterns alternately stacked on a substrate, and extending in a first direction. The semiconductor device includes a semiconductor cap layer on an upper surface of the fin structure, and extending along opposite side surfaces of the fin structure in a second direction crossing the first direction. The semiconductor device includes a gate electrode on the semiconductor cap layer, and extending in the second direction. The semiconductor device includes a gate insulating film between the semiconductor cap layer and the gate electrode. Moreover, the semiconductor device includes a source/drain region connected to the fin structure. The plurality of first semiconductor patterns include silicon germanium (SiGe) having a germanium (Ge) content in a range of 25% to 35%, and the plurality of second semiconductor patterns include silicon (Si).